With rapid development of science and technology, the Digital Subscriber Line (DSL) technology has been capable of providing voice, video and data services on an ordinary twisted pair and, with features including high speed access, low maintenance cost, a capability of making full use of existing networks and safe use, etc, has become one of the most promising and competitive technologies.
The DSL technology has developed to the Second Generation Very-high-bit-rate Digital Subscriber Loop (VDSL2), but the potential of twisted pair has not been fully explored. By expanding frequency spectrum, the latest G.fast technology can provide, on the twisted pair, asymmetrical transmission having an uplink net rate and a downlink net rate both reaching 500 Mbps. This standard has been initiated by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) in 2011, and its first edition of draft is expected to be issued by the end of 2012.
FIG. 1 is a schematic diagram illustrating reverse powered Fiber To The Distribution Point (FTTDP) in the typical application scenario of G.fast according to the related are. As shown in FIG. 1, a access device for the access of fiber to a Distribution Point (DP) is generally deployed in the basement of a premise or at the position of a wire connection hole. Due to the complexity of access environment, it is relatively difficult to power the access device. If a dedicated wire is laid from a public power source to the access device, then systemic deployment cost will be increased. As the distance between the access device and a user terminal is usually within 200 meters, it is possible to reversely power the access device from the user terminal. However, when a plurality of user terminals connected with the access device reversely power the access device, but if there is not traffic between the plurality of user terminals and a network, the user still should power the access device, which undermines user experience. Apart from this, how to guarantee the equality of the plurality of user terminals and the transparency of the power supply for the access device also become urgent problems.